1. Field of the Invention
The present invention relates to an insulated wire having a spiral end to be used in connecting, for example, to a pin terminal of an electronic device, and a method for connecting the insulated wire.
2. Description of the Related Art
In recent years, electronic devices have become increasingly miniaturized.
Therefore, connecting a conductor of an insulated wire to a pin terminal, for example, requires that the connecting part itself be compact and the operation for connecting be conducted in a narrow space.
Furthermore, it is also required that the workability be good, the operating cost be low, and the cost of parts used for connecting be low. In addition, in order to protect the parts to be connected through a pin terminal from heat, the parts must not be heated for a prolonged period of time during the connecting operation. Additionally, in order to prevent the formation of sparks on application of high voltage, the connecting part should have no protrusions, the contact resistance should be small, and the strength of the connecting part should be large enough to prevent from releasing easily.
However, in view of the requirements described above, the connecting methods of the related arts involve many problems. Various connecting methods of the related arts and problems thereof are described below with reference to FIGS. 6A and 6B and FIGS. 7A to 7C. In these figures, numeral 15 denotes a conductor, 16 denotes an insulated wire, 17 denotes a pin terminal, 18 denotes solder, 19 denotes a caulking sleeve, 20 denotes a caulking terminal.
In the connecting method shown in FIGS. 6A and 6B, a tip end of a conductor 15, exposed by removing insulation at an end of an insulated wire 16, is accompanied by a pin terminal 17 as shown in FIG. 6A, and then the pin terminal 17 and the conductor 15 are fixed with solder 18 as shown in FIG. 6B.
This connecting method involves the following problems. The workability is poor because, in order to solder a holding fixture to accompany the conductor and the pin terminal, an operator must be skilled in soldering; poor soldering brings about inferior connection strength. Also, there is a possibility that the pin terminal will be heated during soldering for a protracted time.
In the connecting method shown in FIG. 7A, a conductor 15 exposed by removing insulation at an end of an insulated wire 16 and a pin terminal 17 are inserted into a caulking sleeve 19 respectively from both ends thereof, and the caulking sleeve 19 is crimped from the outside thereof to fix the conductor 15 and the pin terminal 17 inside the caulking sleeve 19.
This connecting method also has problems.
The caulking sleeve 19, which is required for the connection, is expensive, the length of the connecting part becomes elongated because of the use of the caulking sleeve 19, and a space is required into which a crimping tool must be inserted upon making the connection.
In the connecting method shown in FIG. 7B, a caulking terminal 20 having a ring is fixed at a tip end of a conductor 15 exposed by removing insulation at an end of an insulated wire 16. At this time, the conductor 15 and the insulated wire 16 are respectively clamped with claws equipped at two positions on the caulking terminal 20. A pin terminal 17 is inserted in the ring of the caulking terminal 20, and the pin terminal 17 and the ring are then fixed by soldering (not shown in the figure).
This connecting method involves the following problems. After the pin terminal and the ring are soldered, the connection strength is insufficient because the ring is of a single fold; a caulking terminal 20 having a ring, which is required for making this connection, is expensive; and there is a possibility that the pin terminal will be heated for a protracted period of time during soldering.
In the connecting method shown in FIG. 7C, a tip end of a conductor 15 exposed by removing insulation at an end of an insulating wire 16 is wound several times around a pin terminal 17, and the conductor 15 and the pin terminal 17 are then fixed by soldering (not shown in the figure).
This connecting method involves the following problems. Specifically, space is required for winding the conductor; there is a possibility that the pin terminal will be heated for a long time during soldering; and a protrusion of solder is liable to form at the connecting part because soldering is conducted after winding the conductor.
It is an object of this invention to provide a method for easily connecting a conductor of an insulated wire to a pin terminal at low cost while removing, to the extent possible, the problems associated with the related art connecting methods as described above. Another object of this invention is to provide an insulated wire having a spiral end for performing the connecting method of the invention.
The invention relates to an insulated wire having a spiral end produced by a process comprising removing insulation at an end of an insulated wire to expose a conductor; and winding the exposed conductor into a spiral form by 1.5 folds or more to produce a spiral part at an end of the conductor.
The insulated wire having a spiral end can be easily connected to a pin terminal by inserting a pin terminal into a central opening of the spiral part, and fixing the spiral part and the pin terminal with a fixing material, such as solder or a binding agent having a high conductivity.
It is possible that a solder coating may be previously formed on the spiral part of the conductor, and after inserting the pin terminal into the central opening of the spiral part, the spiral part can then be heated to electrically connect the pin terminal and the insulated wire having a spiral end by melting the solder coating. In this case, the heating time is short, and the workability is improved, so that an electronic device, such as a cold cathode tube, to which the pin terminal is connected, is not damaged by heat. Furthermore, the contact resistance at the connecting part can be made small, and the fixing strength at the connecting part can be increased.
In the case where a stranded wire is used as the conductor, it is preferred that the spiral part have a spiral direction opposite to a stranding direction of the stranded wire, whereby unraveling of the stranded wire can be prevented on forming the spiral part.